1. Field of the Invention
The present invention relates to an image data transmission apparatus preferably, preferably used in facsimile apparatus or the like.
2. Description of the Prior Art
In a facsimile apparatus, the original image is read by a one-dimensional contact type image sensor (hereinafter called image sensor) including, for example, a charge coupled device (CCD). In the vicinity of the image sensor of the main body of the facsimile apparatus, an original inlet stretching along the image sensor is formed, and by inserting the originals, the image of which is to be transmitted, into this original inlet, the inserted original is transferred in the direction orthogonal to the longitudinal direction of the image sensor and the original image is read out by the image sensor at the same time.
In such facsimile apparatus, a large original or a bulky original such as a book cannot be inserted into the original inlet, so its image can be neither read nor transmitted. It has been considered to mount a reading unit including the image sensor detached from the main body of the facsimile apparatus so as to read the image of the original, that cannot be inserted from the original inlet, by scanning manually.
In such a case, however, since the original plane is scanned manually, the scanning speed is not always constant. Therefore, when the original plane is scanned at an excessively high speed by the reading unit, the image data transmission processing by the facsimile apparatus cannot catch up with the reading processing by the reading unit, and a reading error may occur. It is therefore necessary to scan the original plane by the reading unit at a considerably low speed. If the speed is extremely low, the image data transmission processing by the facsimile apparatus goes ahead of the reading processing by the reading unit. As a result, in the facsimile apparatus conforming to the standard of Group 3 for document transmission, when there is no longer image data to be transmitted, and when a data blank period lasts for more than 5 second, the transmission is cut off from the telephone line, and the subsequent image data cannot be transmitted.
When transmitting the image data which is by manual scanning of the reading unit on the original plane, it is necessary to first store the read image data in memory, then connect the line with the facsimile apparatus of the destination side, and transmit the image data out from the memory.
However, in order to store all image data to be transmitted first in the memory, a large memory capacity is required, and realtime transmission processing can not be realized, so it takes a relatively long time for image data transmission. Furthermore, the operator must manipulate the operation unit of the facsimile apparatus to specify the reading processing of the image data into the memory, and the controllability of such a facsimile apparatus is extremely poor.